High-level automatic control technology is often applied to industrial robots and machine tools to improve their performance. Examples of automatic control technology include an open loop system and a closed loop system.
In an open loop system, such as a non-feedback system, a sequence control is typically used. This non-feedback system is not often used, though. A closed loop system, such as a feedback system, can be expensive, but is often used in industries due to the ability to accurately compensate for a present value.
A feedback system generally includes a proportional controller, an integral controller, a proportional integral controller, a proportional derivative integral controller, a fuzzy controller, and a fuzzy proportional derivative integral controller. A controller can be used according to system properties, depending on which controller is appropriate. A proportional integral controller and a proportional derivative controller are most often used.
A proportional integral control method is typically used in a non-motorized system. This method has advantages in improving a response time of the system, preventing excessive overshoot, and enhancing stability.
In order to control automatic exposure (AE) of a camera module, a device includes digital control technology to maintain the brightness of an image in the optimized state regardless of the illumination of a light source.
An AE controlling function automatically controls the brightness of an image by considering the light intensity of a subject and its surroundings, and the reflectivity of the subject.
For a digital cameral module, an AE algorithm is often implemented in an image signal processor (ISP) to perform the AE controlling function. The AE controlling function adjusts the brightness level of the subject for each input image frame in correspondence to the illumination change around the subject and the brightness of the subject.
A related art AE algorithm processes feedback signal data before an AE compensation control in an aspect of a signal process. Therefore, this is limited to only compensating for a difference of a target brightness value and a present brightness value.
The related art AE algorithm writes an electrical shutter (ES) value and an automatic gain control (AGC) value with respect to the various brightness values in a database through a great number of experiments. Then, when performing AE compensation, the ES value and the AGC value that correspond to the processed present brightness data are utilized through image signal processing.
However, according to this related art method, memory usage in the ISP increases. Also, it takes a relatively long time to develop various algorithms, and malfunctions often occur in unexpected environments.
Furthermore, AE accuracy is limited because the time for processing an image signal is not taken into consideration.
Thus, there exists a need in the art for an improved device and method for controlling AE.